/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SSplitter.h
Add a slot to the splitter at the specified index Sample usage: SomeSplitter->AddSlot()[ SNew(SSomeWidget) ];
the new slot.
[FScopedWidgetSlotArguments](API\Runtime\Slate\Widgets\Layout\SSplitter\FScopedWidgetSlotArguments) AddSlot ( int32 AtIndex )